Grounding device for a point in a conductive casing

ABSTRACT

The invention concerns electrical units housed in a metal casing comprising a plurality of grounding points. It is characterized in that only one fixed contact and possibly, one mobile or movable contact end piece are permanently installed, the rest of the grounding device is a detachable assembly which can be used, according to needs, at various grounding points.

United States I Patent [1 1 Fournier [451 Sept. 25, 1973 GROUNDING DEVICE FOR A POINT IN A I CONDUCTIVE CASING [75] Inventor: Jacques Fournier, Lyon, France I [73 Assignee; Delle-Alsthom, Villeurbanner,

France [22] Filed: Mar. 16, 1972 [21] Appl. No.: 235,272

[ 30] Foreign Application Priority 'Data Mar. 18, 1971 France 7109563 [52] [1.5. CI 200/48 R, 200/163, 200/82 R, 200/148 B [51] Int. Cl. H0111 21/28 [58] Field of Search 200/163, 148 B, 48

zoo/61.08, 82 R [56] References Cited UNITED STATES PATENTS 3,374,331 3/1968 Brockhaus et a1. 200/163 X 9/1963 Reichardt 200/163 3,238,321 3/1966 Lawwill et al. ZOO/61.08 3,372,622 3/1968 Bullard 200/82 R 3,286,058 11/1966 Perhats 200/82 R Primary Examiner-Herman J. Hohauser Attorney-Richard C. Sughrue et al.

[57] ABSTRACT The invention concerns electrical units housed in a metal casing comprising a plurality of grounding points. It is characterized in that only one fixed contact and possibly, one mobile or movable contact end piece are permanently installed, the rest of the grounding device is a detachable assembly which can be used, according to needs, atvarious grounding points.

, 12 Claims, 6 Drawing Figures PATENTEDsEP25|s7s SHEET 1. OF 2 FIGQ GROUNDING DEVICE FOR A POINT IN A CONDUCTIVE CASING BACKGROUND QE THE INVENTION nism, enabling grounding to be effected at a determined point of the installation. According to whether a possibility of closing is or is not required, operation is fast or slow. In a large electrical unit, the number of points to be grounded can be very high, and if, at each point, a conventional grounding device is installed, the cost of these appliances taken as a whole constitutes an appreciable part of the cost of installating.

SUMMARY OF THE INVENTION The invention proposes to reduce this cost. To do this, it provides an electrical unit housed in a conductive casing, comprising, at several grounding points, permanent fixed contacts (3) which can be connected to ground by means of connecting devices each comprising a mobile or movable contact actuated by an operating mechanism. The invention further includes detachable assemblies (12), provided in a smaller quantity than the number of grounding points. Each assembly includes an operating mechanism which is coupled to the mobile contact. The connecting devices bear against a hole in the said conductive casing providing for the insertion of the mobile contact, inside the space limited by the said conductive casing, until it engages with one of the said fixed contacts.

Preferably, at certain points, at least, where grounding is anticipated, besides the fixed grounding contact, a mobile contact is installed. The independent detachable assembly which includes an operating mechanism is fixed into the mobile contact when it is necessary to effect grounding, and makes it possible to effect grounding at the chosen point. The operating mechanism can be hand controlled or electrically controlled and operate slowly or fast. A large electrical unit will therefore comprise a great number of mobile contacts and a single operating mechanism or a very small number of operating mechanisms. These will be permanently fixed only at the points where grounding is very frequent.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the accompanying diagrammatic figures, examples of implementing of the invention which will enable other characteristics to become apbly intended for providing the connection with the ground of the fixed contact and comprising a rapid spring-actuated closing mechanism released by a catch.

FIG. 3 also shows a sectional view of the detachable assembly assembled on the metal casing, the installation being in the grounding position.

FIG. 4 shows the sectional view of a varied version of a detachable assembly with a spring-actuated rapid closing and opening mechanism comprising a tumbler type neutral point changeover.

FIG. 5 shows the sectional view of a varied version of a detachable assembly with a screw-actuated slow opening and closing mechanism.

FIG. 6 shows the sectional view of a varied version of a detachable assembly with a rapid closing mechanism obtained by means of an explosive.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, a conductor 1, energized, in normal operation, is held, by insulating parts, not shown, inside a metal casing 2 connected to ground. The casing is insulated from the conductor by a gas under pressure having high dielectric rigidity, such as sulphur hexafluoride, which fills the space placed between the conductor and the casing. The conductor 1 supports a fixed contact 3 of the grounding device. A connection piece 4, closed during normal operation by a lid 5, fitted with a seal 6 which provides permanent fluid-tight sealing,

is fixed, preferably by welding, to the casing 2. Inside the connection piece 4, there is a mobile or movable contact 7 of the grounding device, which, in the closed position,. co-operates with the fixed contact 3. This movable contact comprises a tapped portion 8 which will ensure the link with the mobile rod borne by the detachable assembly and connected to the operating mechanism of the grounding device. A sliding seal 9 ensures temporary fluid-tight sealing between the connection piece 4 and the mobile part of the grounding device during the operation of the latter. The seal 9 prevents a leakage of the pressurized gas towards the outside atmosphere, during operation.

The existence of a movable contact 7, in the break position in the connection piece 4, enables connection to the operating mechanism and the grounding operation under pressure without any appreciable loss of gas to be effected. If the movable contact 7 is not, in the break position, in the connection piece 4, and forms a part of the mobile rod borne by the detachable assembly, it is necessary, when the metal casing contains a gaseous medium other than air at atmospheric pressure, to provide a flap or a diaphragm which moves away during the operation. Nevertheless, the latter arrangement is generally more complicated and it will not be described in the examples given, corresponding to preferred embodiments. The holding in position of the movable contact 7 is effected as follows: in all cases, a stop flange 10, forming part of the movable contact 7, avoidsthe outward ejection of the latter under the action of the internal pressure when the cover 5 is lifted off. Moreover, the friction of the seal 9 keeps the movable contact 7 in position, but if it is required to ensure that the movable contact 7 cannot fall inside the casing 2, subsequent to vibrations or for any other cause, a detachable backstay ll fixed by a screw inserted in the tapping 8 of the movable contact 7 is placed against the connection piece 4.

FIG. 2 shows a body 12 of the detachable assembly which will, during a grounding operation, replace the lid 5. The mobile rod 13, having a longitudinal sliding movement, fits onto the movable contact by means of an auxiliary rod 14 which can rotate in the rod 13, and a screw thread 15 which penetrates into the tapped portion 8 of the movable contact 7 when a rotational force is exerted on a square head borne by that rod 14. To enable this screwing of the rod 14 in the movable contact 7, the latter comprises a device not shown, such as a rib or a stud, for example, blocking it during rotation on the connection piece 4. An operating lever 18 pulled at 19 by a spring 20 is fixed at 17 on the rod 13. The other end 21 of the latter is fixed on a nut 22 whose movement is controlled by a screw 23. A catch 24 pulled back by a spring 25, holds a roller 26 and the lever 18. Sufficient fluid-tight sealing for the duration of the grounding between the body 12 and the contact rod 13 is provided by sliding seal 27. Before and during the operation, the body 12, which is itself connected to the contact rod 13 by a sliding contact 29, is connected to the ground electrode of the unit by means of a flexible conductor 28. When operations are frequent, the body 12 can be permanently installed on the connection piece 4. The releasing of the catch 24-26 can be effected by means of a remote-controlled electromagnet not shown.

The operation of the grounding device is as follows. Originally, the installation is in the position shown in FIG. 1, and it is required to ground the conductor 1. The cover and, when it is provided, the back stay 11 of the end fitting are removed. The body 12 of the mechanism replaces the lid 5. By means of the square head 16, the screw thread of the rod 14 is inserted into the tapped part 8 of the movable contact 7, thus making the contact rod 13 and the threaded rod 14 fast for the subsequent closing. The screw 23 is then made to turn so as to bring the screw 22 into the position in FIG. 2, thus ensuring the stretching of the spring 20. By moving the lever 24, the roller 26 is released and the spring becomes slack; the movable contact 7, secured to the rod 13, is inserted into the fixed contact 3 and connects the conductor 1 to ground through the sliding contact 29 of the body 12 through the conductor 28.

The device is then in the state shown in FIG. 3. To disconnect the ground, the screw 23 is made to rotate in the direction causing the movement of the nut 22 towards the right. A strip 30, secured to the screw 23, pushes the lever 18 towards the right and brings the roller 26 back onto the catch by rocking the lever 24, which at the end of the movement of the roller 26, is pulled back by the spring in the position shown in FIG. 2. With this device, closing is rapid and opening is slow.

A locking means, not shown, can stop the spring 20 from being stretched if the body 12 is not assembled on the connection piece 4, and, conversely, can prevent the removal of the body 12 before ungrounding the device.

In FIG. 4, the positioning of the body 12 on the connection piece 4 and the fixing of the contact rod 13 on the movable contact 7 are identical to those in FIGS. 2 and 3, but the catch mechanism is replaced by a tumbler type mechanism. The contact rod 13 is actuated by the operating lever 18 through a connecting rod fixed at 17. The spring 20 is fixed, at one end to 19, on the lever 18 rotating about the rotating point 31, and at the other end to 21, on the nut 22 whose movement is controlled by the screw 23. Starting from the position of the spring 20 fixed by the nut 22, the rotation of the screw 23 moves the nut towards the left, to 22, and stretches the spring along line 19, 20', 22, whose axis passes, then, through the rotation point 31 of the lever 18. By continuing to move the screw 22 towards the left, to 22", the spring becomes a driving spring, drives its fixing point 19 on the lever 18 to 19" and provides rapid grounding by moving the contact rod 13 towards the left. For ungrounding, the rotation of the screw 23 moves the nut 22 towards the right, and when the nut passes the position 22" placed in the extension of 19" and 31, the spring 20 becomes a driving spring and provides rapid opening of the contact rod 13.

For the devices in FIGS. 2 and 4, the driving of the screw 23 can be effected electrically by means of a motor such as that diagrammatically shown at 32 fitted with the required end-of-stroke controls.

The device in FIG. 5, whose mechanism, is more simple, enables slow closing and opening, and can be used only when a possibility of closing the grounding device is not necessary. The contact rod 13 comprises a connection piece 33 internally tapped and crossed by a screw 34. A flange 35 presses against the connection piece 36 which forms a part of the body of the mechanism 12, inside which a smooth part 37 extending the screw 34 turns freely. The rotating of the screw 34 directly drives the contact rod 13 both after closing and after opening.

In the devices in FIGS. 2 to 5, after closing the contact rod 13 cannot return backwards under the action of the gas pressure contained in the casing 2, for the contact rod 13 is held, either by the action of the spring 20, or the screw 34.

The device in FIG. 6 comprises rapid closing under the action of an explosive. As previously, the body of the mechanism 12 containing the contact rod 13, is fixed on the connection piece 4. A threaded plug 38. on which a breech block 40 can be adapted by means of a bayonet joint 39, is fixed on the body 12. This breech block contains a cartridge of explosive 41 (such as the cartridges used in pistols for scaling, for example) whose detonation is caused by a firing pin 42 under the action of a spring 43. This firing pin is released by the breaking ofa catch 44, determined by the operating of a lever 45. The explosive is used to accelerate the rod 13 initially, but, to avoid possible breakages, due to too great a power, at the end of the stroke, a vent 46 enables the removal of the excess gases.

The contact rod 13 being able to move freely, and the pressurized gas in the casing 2 tending to push it back into the opening position, it is necessary to hold it in the closing position as soon as the latter is reached, a spigot 47 pushed by a spring 48 locks the contact rod 13 as soon as it is in the closing position, this corresponding to the instant when its end 49 passes the position of the spigot 47. The locking of the rod 13 by the spigot 47 can be keyed by a bolt 50.

The closing by the device in FIG. 6 is effected as follows. After removal of the lid 5 and, if it is provided, of the back stay 11, the body 12 is adapted on the connection piece 4, and the plug 38 is unscrewed. The rotation of rod 14 drives the threaded portion 15 into the tapped portion 8 and makes the movable contact 7 secured to contact rod 13. The plug 38 is put back in its place on the body 12, the bayonetjoint 39 is unscrewed and the breech block 40 is removed; the cartridge 41 is then placed in its recess, then the breech block 40 is put back in its place and the catch 44 is cocked. The lever 45 is then operated breaking the catch 44. The firing pin 42 is actuated and makes the cartridge 41 explode. The gases given off cause the closing of the grounding device by moving the contact rod 13 towards the left. The vent 46 removes the excess gas, the spigot 47 provides for the locking of the rod 13in the closing position and the bolt 50 keys this locking means.

For the opening of the grounding device, the bolt 50 is removed and the spigot 47 is pulled upward. Under the pressure of the gas in the casing, the rod 13 moves towards the right. If, however, the friction due to the sliding of the rod 13, the sliding contacts 29 and the seal ring 27, give an effort greater than the effort due to the pressure of the gases, the plug 38 is unscrewed, an extension is fixed onto the rod 14 and the mobile contact is pulled by hand towards the right.

When the conductor returns to the normal ungrounded state the contact rod is in the opening position and the rod 14 is made to rotate, thus detaching its threaded portion 15 from the movable contact 7 which is in place in its recess in the opening position. The body 12 is separated from the connection piece 4 and if required, the back stay 11 is fixed in position and the lid 5 is put back in its place.

What is claimed is:

l. An electrical unit housed in a conductive casing comprising:

a. a first plurality of grounding points each grounding point including a permanent fixed contact which can be connected to ground;

b. a second plurality of connecting means mounted on said casing each connecting means including movable contact means for engaging one of said fixed contacts; and

c. a third plurality of detachable assembly means engaging said connecting means each assembly means comprising a body member coupled to said connecting means and an operating mechanism means for engaging a portion of said movable contact means wherein movable contact means is moved into engagement with said fixed contact means by said operating mechanism means whereby said detachable assembly means are connected to ground through said fixed contact means.

2. An electrical unit as set forth in claim 1 wherein said connecting means includes a connecting piece fixed to said casing and wherein said movable contact means are mounted in said connecting piece.

3. An electrical unit according to claim 2 wherein said connecting means further includes a first seal ring between movable contact means and said connection piece.

4. An electrical unit as set forth in claim 1 wherein said operating mechanism means comprises an auxiliary threaded rod means for engaging the movable contact means.

5. The electrical unit as set forth in claim 1 wherein said detachable assembly means includes a second seal ring around a portion of said operating mechanism means.

6. The electrical unit as set forth in claim 2 wherein said movable contact means includes a flange which abuts said connection piece under the action of the internal pressure in said conductive casing.

7. The electrical unit as set forth in claim 2 further including removable lid means for covering all of said second plurality of connection means which are not coupled to said third plurality of detachable assembly means.

8. The electrical unit of claim 1 wherein said operating mechanism means includes a spring controlled by a catch for causing the rapid grounding of said grounding point when said catch releases said spring.

9. The electrical unit of claim 1 wherein said operating mechanism means includes a spring controlled by a tumbler means for causing the rapid grounding of said grounding point when said tumbler means releases said spring.

10. An electrical unit as set forth in claim 1 wherein said operating mechanism includes an explosive means for moving said movable contact into contact with said fixed contact when said explosive means detonates whereby said grounding point is grounded.

11. An electrical unit as set forth in claim 10 wherein said operating mechanism includes a vent means for limiting the action of said explosive means at the end of the stroke of said movable contact.

12. An electrical unit as set forth in claim 11 wherein said operating mechanism further includes spigot means for locking said movable contact in the 

1. An electrical unit housed in a conductive casing comprising: a. a first plurality of grounding points each grounding point including a permanent fixed contact which can be conNected to ground; b. a second plurality of connecting means mounted on said casing each connecting means including movable contact means for engaging one of said fixed contacts; and c. a third plurality of detachable assembly means engaging said connecting means each assembly means comprising a body member coupled to said connecting means and an operating mechanism means for engaging a portion of said movable contact means wherein movable contact means is moved into engagement with said fixed contact means by said operating mechanism means whereby said detachable assembly means are connected to ground through said fixed contact means.
 2. An electrical unit as set forth in claim 1 wherein said connecting means includes a connecting piece fixed to said casing and wherein said movable contact means are mounted in said connecting piece.
 3. An electrical unit according to claim 2 wherein said connecting means further includes a first seal ring between movable contact means and said connection piece.
 4. An electrical unit as set forth in claim 1 wherein said operating mechanism means comprises an auxiliary threaded rod means for engaging the movable contact means.
 5. The electrical unit as set forth in claim 1 wherein said detachable assembly means includes a second seal ring around a portion of said operating mechanism means.
 6. The electrical unit as set forth in claim 2 wherein said movable contact means includes a flange which abuts said connection piece under the action of the internal pressure in said conductive casing.
 7. The electrical unit as set forth in claim 2 further including removable lid means for covering all of said second plurality of connection means which are not coupled to said third plurality of detachable assembly means.
 8. The electrical unit of claim 1 wherein said operating mechanism means includes a spring controlled by a catch for causing the rapid grounding of said grounding point when said catch releases said spring.
 9. The electrical unit of claim 1 wherein said operating mechanism means includes a spring controlled by a tumbler means for causing the rapid grounding of said grounding point when said tumbler means releases said spring.
 10. An electrical unit as set forth in claim 1 wherein said operating mechanism includes an explosive means for moving said movable contact into contact with said fixed contact when said explosive means detonates whereby said grounding point is grounded.
 11. An electrical unit as set forth in claim 10 wherein said operating mechanism includes a vent means for limiting the action of said explosive means at the end of the stroke of said movable contact.
 12. An electrical unit as set forth in claim 11 wherein said operating mechanism further includes spigot means for locking said movable contact in the grounded position. 